The objectives of this proposal are to characterize the mechanisms involved in the tissue-specific assembly of corneal extracellular matrices. Specific interactions regulate fibrillogenesis and matrix assembly during development. Corneal-specific extracellular matrix assembly is a multistep process and the coordinate regulation of the individual steps is essential for normal development and growth. The acquisition of this foundation will provide the basis for understanding of repair/regeneration, pathobiology and eventually permit the modulation of these processes. The specific aims of this project are: (1) to characterize the specific steps in corneal fibrillogenesis regulated by collagen type I/V interactions; (2) to determine the role of the leucine-rich repeat proteoglycans, decorin and lumican, in corneal fibril and matrix assembly; and (3) to analyze keratocyte-matrix interactions in regulation of tissue-specific matrix assembly and cell behavior. We will utilize transgenic mice deficient in type V collagen, type VI collagen, decorin or lumican with structural, morphometric, molecular, biochemical and immunochemical approaches. Our hypothesis is that during the initial assembly of collagen molecules into the corneal fibril, type V collagen nucleates initial fibril assembly and that the high concentration of type V collagen in heterotypic fibrils favors initiation of new fibrils rather that continued growth of existing fibrils. We hypothesize that the temporal and spatial expression patterns of leucine-rich repeat proteoglycans confer developmental stage-specific interactions that regulate different steps in fibrillogenesis and also are important in mediating higher order matrix assembly. We hypothesize that interactions with the developing extracellular matrix determine keratocyte topography and orientation. This ultimately determines how specific stages in matrix assembly are compartmentalized within the developing stroma. Factors that influence cell behavior would be expected to have a profound effect on the cell's ability to regulate extracellular events. An understanding of corneal development, transparency, hydration, as well as disorders such as edema, wound healing and some dystrophies requires the elucidation of the factors involved in the regulation of collagen fibrillogenesis, matrix assembly and tissue interactions. The proposed studies will lead to an understanding of these processes.